High speed, high resolution laser based scanning systems have been utilized in non-impact printer products. Such scanning systems offer higher speed and resolution than can be cost effectively achieved using electromechanical printers.
Such systems usually incorporate a modulatable beam of light which can be deflected onto a target by a movable deflection member such as a mirror or prism. Such systems can be operated to create a raster formed of multiple scan lines. Text images can thus be generated on a line-at-a-time basis.
Higher resolution and higher speed require that the beginning and ending points of each the scan lines line up with the corresponding points of the other scan lines of a given raster. Where the light beam deflection mechanism is a self-resonant galvanometer, various systems have been developed for the purpose of improving the alignment of scan lines' starting and ending points.
One such system is disclosed in Schoon U.S. Pat. No. 4,630,223 entitled "Scanner Amplitude Stabilization System". A second system is described in Schoon U.S. Pat. No. 4,686,363 entitled "Self-Resonant Scanner Biasing System" which patent is incorporated herein by reference.
While the known systems provide improvements to scanning repeatability, nevertheless, as scanning speeds increase and resolution requirements increase, a higher degree of scan line stability is desired than has been provided by the previously known systems. Preferably, enhanced scan line stability can be achieved in a cost effective system which does not require complex mechanical modifications to the scanner nor additional complex control circuitry.